Weird HDMI dropout problem

Discussion in 'Cables & Switches' started by EENJEC, Oct 11, 2017.

  1. EENJEC

    EENJEC
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    OK, a very weird problem:
    I'm connecting a PS4 and Xbox One (S) to both a BENQ projector and an LG TV via the two outputs on a Denon Receiver. There is a (necessary) long cable run (15m) from Denon to TV, and shorter to the projector (5m). I get picture dropouts on the projector when using either source EXCEPT when the tv is either turned on, OR (and here's the weird part), when the TV mains cables is unplugged and then plugged in again. Another source (a Zappiti box) work fine and doesn't show this behaviour.
    I don't think its an HDMI ground loop problem as everything is now running off the same extension cable, but the behaviour when unplugging and then plugging in the TV again is pretty baffling to me.
    (and, in full disclosure, I'm a Professor in Electronic Engineering!). It's as if changing the grounding somehow shorts some charge in the TV which then fixes the issue in the projector, which then returns over a few hours or so. Banging my head against the wall on this one, any help or thoughts much appreciated.
     
  2. ChuckMountain

    ChuckMountain
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    How long and frequent are you drop outs ?

    Welcome to the wonderful world of HDMI :)

    If its a fairly short drop out it is quite possibly the HDCP handshake and reestablishing. This could be due to the length of the 15m cable. Does it ever drop out after fully disconnecting the 15m cable ?

    I have had a short faulty cable that has caused a similar issue on a splitter whereby you would get drop out because the cable was causing the HDCP to fail\retry every so often.

    The Zappiti box does use HDCP but might be less susceptible to it.

    Incidentally even though HDMI has a hot plug detector its not recommended to do so
     
  3. EENJEC

    EENJEC
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    Thanks for the response. Some answers: On the XBox the dropouts are short, while on PS4 they are long (sometimes it doesn't handshake at all and the projector just hunts for a signal, until I turn the TV on or switch its plugs, in which event it locks on immediately! It's only on the projector (the shorter HDMI cable) that the dropouts appear, and they're still there after swapping out its HDMI cable so I can't blame that. The mystery thickens!
     
  4. ChuckMountain

    ChuckMountain
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    Have you swapped out the long cable though?

    HDMI cables are not very reliable at 15m and will only pass certification up to 8m anyway.

    Is the amp a mirror splitter or is each HDMI output capable of outputting something different. Depends on which model you have I guess?

    I have 15m cable in my setup and whilst it works fine it does exhibit somethings others don't like for example coloured snow occasionally when switching inputs
     
  5. EENJEC

    EENJEC
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    That’s difficult to do as it’s in ducting. If I disconnect it from TV the problem goes away. But the TV signal from either source is fine on the TV, it’s just the projector signal which glitches. Could noise introduced on the 15m cable be being fed back to the recover perhaps, so that it affects the other output? I can’t see why that wouldn’t affect the TV too though... it’s a simulateous dual output model in mirror mode (x4200w).
     
  6. ChuckMountain

    ChuckMountain
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    The problem with HDMI at the limits are there could be various causes.

    How's this as an idea?

    If the TV is powering down\in a lower power state, interference on the HDMI 15m cable could cause the HDCP to trip up unnecessarily. When its powered on its talking to the amp all the time so its not necessarily going to suffer the same "interference"

    If you have the TV on and PJ off then power the PJ off does the TV blank for a bit?

    I think you can disable HDCP in the PS4, see if that makes any difference or not?
     
  7. andy1249

    andy1249
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    If you can only mirror the signal on both HDMI outputs of the amp then both outputs are effectively a splitter.

    With a splitter its the EDID signal that is critical for the handshake setup and is common to both lines , as the EDID must gather setup info for both displays and find a common setup for each.

    The 15 meter cable will be attenuating this signal and most likely corrupting it.

    With the screen at the end of the 15 meter cable powered off , its EDID chip is being powered by the HDMI 5v line, with it on , its EDID circuitry is powered by its own PSU.

    That is almost certainly where the problem lies, the EDID handshake routine that is common to both screens is being affected by the 15 meter cable.
    Cables are only guaranteed to be reliable up to 8 meters.

    For runs longer than 8 meters look at HDMI over category solutions ( HDbaseT is best) or HDMI over fibre. ( HDMI over fibre is relatively new and very expensive)
     
  8. ChuckMountain

    ChuckMountain
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    I wondered that too, but any reason why one source works and two don't?
     
  9. Joe Fernand

    Joe Fernand
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    CEC - ensure HDMI Control is disabled on all devices.

    AVR - can you toggle its Output between A, B and A+B.

    15m HDMI cable - as others have said long cables can be problematic, there are more reliable optionS, such as Fibre or Hybrid Fibre HDMI, at 15m if you can replace your Standard HDMI cable.

    Interactive - as Per Andy’s post HDMI has background Comms. going all the time.

    EDID Manager - you could try installing a powered device on the Display end of the long Cable, the DR HDMI by HDfury is a good option.

    Joe
     
  10. andy1249

    andy1249
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    Variations in signal output strength exist between sources over and above the minimum required by the HDMI spec.
     
  11. ChuckMountain

    ChuckMountain
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    Yes realise that but is the amp just passing it through? All sources are going through the amp, therefore I would have thought it would have been the amp supplying the +5V line rather than the source?
     
  12. andy1249

    andy1249
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    5v yes, the amp will be supplying that.
    EDID /DDC line signals on passthrough is another thing.

    For troubleshooting and verification the 15 meter should be swapped out.
    The replacement doesnt have to run through the wall for troubleshooting purposes.
    It will prove yes or no whether the 15 meter cable is the problem.
    How to deal with the in wall cable can be sorted if it proves to be the issue.
     
  13. stevelup

    stevelup
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    You could try setting 'Video Output' to Monitor 1 or Monitor 2.

    I'm not exactly sure how this works on the Denon. It will either use the selected output exclusively (and disable the other one), or it will just use the EDID data from the selected monitor.

    Either way, that may solve your problem. If it's the first option, well, that's a bit of a pain because you'll constantly need to swap it each time you use the projector. If it's the latter, you may just find your problem goes away permanently (assuming both your display devices have broadly the same capabilities of course!)
     
  14. dannnielll

    dannnielll
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    Don't forget about reflections in the cables. Any kinks in the cable cause changes in the characteristic impedance and create parasitic pulses., With a longer run these can drop outside the time tolerance band and increase bit error rates.
     
  15. EENJEC

    EENJEC
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    Swapping the 15m cable for a shorter run (7.5m) seemed to improve matters, so I’m now going to try an HDF Integral on the TV end of the 15m cable as a hopefully permanent fix. Will report back once it arrives.
     
  16. Joe Fernand

    Joe Fernand
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    The 'cliff' edge tends to kick in at 8m with a copper cable - ensure you use the external PSU with the Integral.

    Joe
     
  17. EENJEC

    EENJEC
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    Thanks, I will. I still find it odd that the cable is fine passing 4K rgb from the PS4 but apparently unable to maintain a good EDID link back to the source unless the TV is powered on. Is that common?
     
  18. Joe Fernand

    Joe Fernand
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    Lost me there :)

    HDMI is a fully 'interactive' communication bus so anything on your system can play its part in delivering a reliable and stable solution.

    Projectors can be more temperamental than Displays and older Displays can be more temperamental than current Displays.

    We supply all manner of cables and fixit box's (inc. HDFury) - given a choice if I have to do a 15m cable run I would be going with a Hybrid Fibre solution.

    Joe
     
  19. EENJEC

    EENJEC
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    Update: the Integral arrived. It solves the original problem of dropouts on the projector when inserted at end of the long cable run to the tv, but has now introduced a new problem!
    The Xbox One S now says the TV cannot do 4K at 60 Hz (with projector off), whereas when I remove it this problem goes away and it correct reports it as 60 Hz 4K capable. Worse, I can't connect to the integral with the iOS app, and their firmware page hosting software for the PC link is down. Feeling like a waste of £!60 at the moment. Any more ideas?
     
  20. Joe Fernand

    Joe Fernand
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    iOS APP - simply toggle BT Off/On on your iOS device, open the App and hit Connect. Don't try and 'pair' the Integral in the iOS BT settings.

    XB1S - can be a pain. Are you powering the device fully Off (at the wall) before introducing it into the system?

    XB1S - are you going in to the same Input on the TV when trying with/without the Integral?

    Joe
     
  21. EENJEC

    EENJEC
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    SOLVED: Further update: The HDF Integral wasn't set to Bluetooth input so the iOs app couldn't connect. All now working and fine. Was able to change passthrough EDID. Now passing 600 MHz 4:4:4 nicely even after the 15m run from all source (PS4, XBS, Zappiti), and projector output appears stable even when TV is turned off. Many thanks everyone!
     

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